1. Field
Provided is thermoelectric materials including coating layers having a high performance index, methods of manufacturing the thermoelectric materials, and thermoelectric devices including the thermoelectric materials, and more particularly, thermoelectric materials including coating layers that exhibit improved thermoelectric performance, methods of manufacturing the thermoelectric materials, and thermoelectric devices including the thermoelectric materials.
2. Description of the Related Art
In general, thermoelectric materials are used in active cooling and waste heat power generation based on the Peltier effect and the Seebeck effect. The Peltier effect is a phenomenon in which, as illustrated in FIG. 1, phonon (heat) moves along with charge carriers (holes of a p-type material or electrons of an n-type material) when a current is made to flow through the materials, and thus cooling and heating occurs at each end of the materials. The Seebeck effect is a phenomenon in which, as illustrated in FIG. 2, charge carriers move along with heat (phonon flow), when temperature gradient is provided by an external heat source, and thus electric current flows through the materials (power generation).
The major advantages of cooling using a thermoelectric material are its lack of moving parts or circulating condensing liquid, its thermal controllability, and its small size. Therefore it is regarded as an environmentally friendly cooling method. The thermoelectric active cooling can be applied in refrigerant-free refrigerators, air conditioners, and various micro-cooling systems.
In addition, thermoelectric materials can be used to convert heat energy to electricity based on the Seebeck effect. Thus, waste heat can be collected for higher energy efficiency in many applications, including motor vehicles.
The performance of the thermoelectric materials is evaluated using a dimensionless thermoelectric figure of merit ZT defined by Equation 1.
                    ZT        =                                            S              2                        ⁢            σ            ⁢                                                  ⁢            T                    k                                    〈                  Equation          ⁢                                          ⁢          1                〉            wherein S is a Seebeck coefficient, a is an electrical conductivity, T is an absolute temperature, and k is a thermal conductivity.
To increase the ZT, a large Seebeck coefficient, high electrical conductivity, and low thermal conductivity are essential.